A site I've long used. Run by a regular contributor to RailUK Forums.
He knows his stuff.
I concur.
The owner (Mike) helped me out when
Oyster▸ muddled up multiple journeys on the same day. Neither my local station or the Oyster helpline were able to compehend what journeys I had actually made (despite touching in and out correctly, plus all the pink validators at interchange stations) or why I was charged as I was.
Mike explained this was due to an emergency OSI (out of station interchange) which linked three journeys into one. But as the maximum time limit expired several times through this one long journey, I ended up being charged four incomplete journey maximum fares (around 4x^7, instead of 3x^1 fare for the actual journeys made).
My understanding is that fare calculation is much better on contactless cards as journeys are processed in the back office, where there is no time constraint on computing what the correct fare should be. As it stands with Oyster cards, the barrier calculates your fare on the touch. A full calculation would potentially cause congestion at the gateline. I'm told Oyster will also be switching to the back office processing at some point, but not sure when this will start.